Jupiter will reach opposition on July 14.
See the end note about enlarging illustrations.
The moment when the great planet is in the opposite direction from the Sun is 8 hours by Universal Time. This is 2 AM in, for instance, the Central time zone of North America. So our sky scene is for the nearest evening, Monday July 13, just a few hours before the exact opposition.
Because Jupiter is opposite to the Sun, it rises about sunset. This time, it is accompanied in the remote background by invisible Pluto; and followed, a few degrees later, by Saturn, whose turn at opposition will come on July 20. At the picture time, Jupiter has reached 10° above the horizon. As the night goes on, the planets will climb to the meridian of the sky at midnight.
The short arrows through the symbols for the planets represent their movement over five days. They are retrograding – moving slowly back westward – during the time, centered on opposition, when Earth is overtaking them.
Because Jupiter is only about a quarter of a degree south of the ecliptic (through which it descended on Feb. 26), it is almost exactly at the point we have marked as the “anti-Sun.” And it is not far past the solstice point, where the Sun is at the December solstice – the most southerly point of the ecliptic. This is one of the most southerly oppositions in Jupiter’s twelve-year cycle.
The constellation boundaries are painted on the inner surface of an imaginary sphere 6 astronomical units (Sun-Earth distances) in radius. The yellow lines are sightlines from Earth to Jupiter at the dates of opposiyion.
The picture is large, so it may appear at low resolution on your screen. So I have made from it a PDF, which you should be able to enlarge and explore as much as you like (using the hand and magnifying tools in Adobe Acrobat).
Roughly, Jupiter goes around the Sun in 12 years, so that it spends a year in each of the 12 constellations of the zodiac. And each opposition is a month later, as Earth gets around to its next overtaking of Jupiter, so that they are 13 months apart. Thus, 2020 June opposiyion in Sagittarius; 2021 July in Capricornus; and so on. An opposition falls in December 2024, therefore spills over the end of December 2025 into January of 2026.
This simple pattern is irregularized in two ways:
Jupiter gets around the Sun a little faster: the period of revolution is 11.85 years. That’s why in the diagram I omit the path for 2031: it would slightly overlap that for 2020.
And the astronomically defined constellations are not equal 30°-wide segments like the corresponding astrological “signs.” Virgo is wide, Libra and Aries are relatively small, and Scorpius is mostly south of the ecliptic, a stretch of which is in Ophiuchus. I use huge Ophiuchus as a foreground window into my imaginary sphere.
Here are the movements of Jupiter’s four great “Galilean” satellites in the first six hours of the day of the opposition (that is, from 0 to 6 Universal Time):
The largest, Ganymede (satellite III), moves out from behind the planet. Io (I) is about to pass in front of the planet. Callisto (IV) has just turned back from its extreme elongation. Ecliptic north is at the top. The satellites are exaggerated 5 times in size.
This opposition is, in the cycle from now to 2032, the second southernmost (declination -21°56′, exceeded only by 2031 June 1, -22°48′); fairly near to Earth (4.14 a.u., compared with 3.95 in 2022 and 4.45 in 2029); among the brightest (magnitude -2.8, as compared with -2.9 at the next three oppositions and slightly dimmer -2.5 at some others).
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ILLUSTRATIONS in these posts are made with precision but have to be inserted in another format. You may be able to enlarge them on your monitor. One way: right-click, and choose “View image”, then enlarge. Or choose “Copy image”, then put it on your desktop, then open it. On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping and dragging with three fingers). Other methods have been suggested, such as dragging the image to the desktop and opening it in other ways.
There is a possibility that Jupiter will occult several of Saurn’s moons at the tine of the Great Conjunction, 17.15 hrs, UT 21/12.
You used opposiyion twice Google has it
Thanks Guy. Such a wealth of astronomical beauty these recent nights — Jupiter and Saturn, the Moon and Mars, Venus and Aldebaran, Comet NEOWISE!
Unfortunately the southerly declination and low altitude of Jupiter and Saturn, coupled with the corona virus pandemic, have limited my opportunities to see them through a telescope. From the back yard I’ve got a couple of narrow windows between trees and buildings that only last for about 15 minutes each. Normally I would carry the telescope to the playground around the corner, but it’s surrounded by the tents of homeless people, and I just don’t feel safe. And my astronomy club has cancelled our monthly star parties on Mount Tamalpais. So I make do with binocular views from the back steps and occasional lucky shots through the telescope when everything lines up, the sky is clear, *and* I’m awake.
Last night through binoculars Io, Europa, Ganymede, and Callisto were lined up left to right to the west of Jupiter. Quite a nice coincidence to see the moons in order of true distance from Jupiter. I play a little game with myself, trying to identify the moons by sight before I check the corkscrew diagram in Sky & Telescope magazine. Ganymede is noticeably brighter than the other moons, and Callisto ranges much farther from Jupiter than any of the other moons, so I was pretty sure about them. I took a hopeful guess about Io and Europa, and turned out to be right.
I had an amazing view of Jupiter and Saturn when walking between Binsey and Oxford last night at about 2330.i was able to test if my 5×10 Zeiss miniquick monocular can show Jupiter’s moons,it can!well I saw 3 through it I suppose that the 4th was round the back.
Thank you for the ingenious diagram of the oppositions of Jupiter. The movements of the moon, stars and planets appear complex but you make it easy to understand.
Very notable once in several millenia occurrence on 21/12 this year, the closest conjunction, 6′ of arc, between Jupiter and Saturn since well before Christ, to be rivalled in 2080, but then only suitably placed for observation in the Southern Hemisphere, cf 02/1961.